Overall Stability Analysis Of Tapered Simply-supported I-Beams

The benefits of using the tapered member are that the internal force distribution happens to coincide with the distribution of the cross section along the length. The tapered member can meet the moment in the same direction. Under the precondition of meeting the strength requirements, tapered member can reduce the consumption of steel, reduce the structural weight, and make the structure form lighter and more attractive. In the design process, the steel structure stability is one of important issues that must be considered.There are two steel structure stability theory, traditional theory and newer theory. The traditional theory is the foundation of overall stability of monosymmetry I-beams in Code for design of steel structures (GB 50017-2003). In this paper, a formulation of critical moment of tapered simply-supported I-beams is obtained on the foundation of each theory. Through the comparison with the finite element calculation results, the formulation of traditional theory will lead to larger errors, and the newer theory will lead to incorrect results.In this paper, there are three different component geometries for the overall stability analysis of tapered simply-supported I-beams. Not only the variation of flange width but also the variation of section height has been considered when analyzing the overall stability of monosymmetry I-beams. Flange width has changed by strengthening the compression flange and strengthening the tensile flange. Uniform load on the top flange, uniform load on the bottom flange, concentrated load on the top flange, concentrated load on the bottom flange have been considered in the analysis of the overall stability.According to the results of finite element analysis, the critical load has converted to the critical moment, and the tapered coefficient of tapered simply-supported I-beams has been calculated too. Based on the regressive computation of the results of the finite element analysis, the paper offers the design formula to calculate the tapered coefficient of tapered simply-supported I-beams. Then the paper offers the design formula to calculate the overall stability of tapered simply-supported I-beams. The study of this paper can serve as some reference for the setup of the formula in the codes for design of steel structures to accurately calculate the overall stability of tapered simply-supported I-beams and for the engineering practice. Because the overall stability factor of I-beams strengthening the tensile flange is not given in the Code, the proposed formula can only used when calculating the overall stability of I-beams strengthening the compressing flange.